Idea: Inductively charging a wireless mouse Monday, July 9th, 2007
Posted by carltonstedman in ece, ideas, projects, wireless power.add a comment
So, had an idea for a project. Yes, been done before, but thought it would be a good exercise, at the very least. There are patents out for this type of thing and even a couple of commercial products. But here’s the project goal: Design a wireless mouse battery charger fitting in a mouse pad. Need to do some more research before I can make some formal specifications, but here’s more info on the concept:
- The batteries inside the mouse must be rechargeable.
- When the mouse is on the mousepad, the internal batteries are being charged up.
- The mousepad is powered from the 5V’s off a USB.
- Inductive power transmission is used.
Here’s the gist on inductive power transmission:
- Method for wirelessly transmitting power through the air.
- Primary coil’s voltage is reflected on to the secondary coil, acting as an air-core transformer.
- Losses (through the air) are probably substantial.
I don’t expect this to be the most efficient thing in the world (at least, not at first). Largely, it is a learning experience, strengthening my understanding of magnetics (which is really just a hand-waving at best right now), and something fun to do. I plan on winding my own coils and using minimal money. The primary coil will be in the mousepad. The secondary coil will be in the mouse. The mousepad, unfortunately, *will* need to be plugged in. Either a spare USB port can be used (at first) or I can grab the +5V out of the transmitter, so it only uses one port (eventually).
Hopefully, I can find a mouse with an internal battery charger. If not, I may need to construct a simple switched battery charger, using the secondary coil, or get a cheap IC. I’d rather design my own, if possible, also as a learning experience, if using NiMH batteries. I think I’d stick with an IC (maybe I could get a sample) if it uses Li-Ion. Even better would be if the charger was internal to the mouse itself and I could just supply the voltage with the coil.
I plan on simulating/modeling this project, especially the magnetics. I would like to learn more about magnetic parasitics and model them, such as core losses, winding resistance, et cetera.
Would be a fun project!
